This invention relates to surveillance systems and, in particular, to an apparatus for and method of storing video data in a video surveillance system.
Archiving the video data gathered by video surveillance systems has been a challenge because of the large amount of data involved. In many instances this data may be stored for months or even years. With MPEG compression algorithms and the increased capacity of today's disk drives, the problem has been reduced, but it is far from being solved. In multi-channel applications, the storage problem is compounded by the number of channels.
Current digital video recorders have two types of storage, namely, short-term and long-term. In most applications the short-term recordings are done with the maximum field rate to get full-motion video. All short-term available information is stored in a relatively small circular buffer. All video is stored at full-frame rate for the required period of time and then removed from the short-term buffer and put into another file for long-term storage. The file is either archived as originally recorded, which requires a large amount of long-term storage resources, or the file is processed to reduce the amount of data that is stored in archive. Processing the file before long-term storage requires that the file be reloaded and pruned in some way to provide a smaller file for archiving. This reloading and pruning process requires significant system resources and can seriously hamper the performance of the digital video recorder in recording current real time data and performing other real time operations.